A put, just like a call, has a few great upsides: you can’t lose more than you spend on the contract, your max profit is unlimited and it is easy to understand when you make money. What makes a put different than a call is that a put makes money when a stock goes down in price; it’s pretty much the opposite of a call in this regard.
The goal of buying a put is to sell when it is ITM, as when it is out of the money, it expires for no profit. To see what happens on the opposite of buying a put, check out 3.5, Selling Puts on Step Up to Options.
If you’re interested in trying the trading platform you see in Step Up To Options, you’ll find it at a new home.